Sooty Tern

The Sooty Tern is one of the most abundant and widespread tropical seabirds, nesting in enormous colonies on remote oceanic islands and otherwise living almost entirely on the wing over open ocean. Its loud, incessant calls at breeding colonies gave rise to the nickname "wideawake tern."

Appearance

Adults are strikingly patterned, with sooty blackish-brown upperparts, crisp white underparts, a black cap, and a white forehead patch that does not extend behind the eye. The bill and legs are black, and the deeply forked tail has white outer edges. Juveniles are entirely dark brown with pale spotting above.

Key field marks

• Sharp, high-contrast blackish-brown upperparts against white underparts
• White forehead patch that stops at the eye, unlike the longer eyebrow of Bridled Tern
• Long, deeply forked tail
• Almost never seen swimming on the water; spends nearly all its time on the wing

Similar species

Bridled Tern is very similar but paler grayish-brown above (not sooty black), with a white forehead patch that extends as a thin stripe behind the eye, and a pale collar around the hindneck. Sooty Tern looks blacker and more contrasty overall, especially in good light.

Habitat and range

Sooty Terns breed in vast colonies, sometimes numbering hundreds of thousands of pairs, on remote tropical and subtropical islands across the Atlantic, Indian, and Pacific Oceans. Outside the breeding season, adults and especially juveniles range widely over open, warm tropical seas and are rarely seen from land.

Migration

Non-breeding birds, particularly immatures, may remain continuously airborne over the ocean for years before returning to land to breed, an extreme example of a pelagic lifestyle. Storms occasionally displace individuals far inland, resulting in unusual sightings away from the tropics.

Behavior

Sooty Terns feed by dipping to the sea surface in flight to snatch small fish and squid, rarely landing on the water since their plumage is not well waterproofed for prolonged swimming. They often forage over schools of tuna or other predatory fish that drive prey to the surface.

Voice

The call is a distinctive, far-carrying "wide-awake" or "ker-wacky-wack," given almost continuously at breeding colonies, day and night.

Nesting and breeding

They nest in dense colonies on the ground, laying a single egg in a shallow scrape with little or no lining. Both parents incubate and feed the chick, which fledges after about two months but may not breed itself until several years old.